In association with the transition to terrestrial digital broadcasting in recent years, display devices capable of displaying a super high definition image are being developed. For preventing the image quality of the super high definition display devices from being impaired, the surface of the display device is demanded to have a capability of preventing outside light from being reflected.
Major examples of the measure for preventing outside light from being reflected include an antiglare treatment for reducing specularly reflected light with surface unevenness, and an antireflection treatment for reducing the reflectance through an interference effect of a multilayer thin film. In recent years, the antireflection treatment, which is easy to provide a high-quality image, is being brought into the mainstream.
The reflectance and the coloration can be reduced more by increasing the number of layers of the multilayer thin film, but most products utilizes an interference effect of two to four layers in view of the cost-benefit performance. Examples of the antireflection film of this type include one described in PTL 1.
In recent years, even an antireflection film utilizing an interference effect of two to four layers is demanded to have an ultra low reflectance of 0.50% or less for preventing the image quality of the super high definition display device from being impaired.
In association with the super high definition display devices achieved in recent years, users are not concerned by pixels even in display devices having a large screen, and consequently display devices having a large screen are being further spread. In the display device having a large screen, the outgoing angle becomes large at the right and left ends of the screen even though the screen is viewed from the front. In a display device having a touch-sensitive panel represented by a tablet type portable information terminal, the outgoing angle may become large at the right and left ends of the screen in some cases even though the display device does not have a large screen since the distance between the screen and the eyes of the user is short (for example, in the case where the display device is used in the lateral position). Furthermore, in a display device having a convex shape, the outgoing angle becomes large at the right and left ends thereof. Accordingly, the uniformity in color over a range having various outgoing angles (which may be hereinafter referred to as “color uniformity”) is receiving increasing attention.
The reflectance and the coloration of the antireflection reflection film having a multilayer thin film are managed by the specularly reflected light of light with an incident angle of 5 degrees for reducing the reflectance and the coloration in the front direction. However, even though the specularly reflected light of light with an incident angle of 5 degrees shows suppressed values for the reflectance and the coloration, the color uniformity may be insufficient in some cases.